On a jib crane vehicle, a jib is extended forward from a distal portion of a top boom of a telescopic boom when the jib is used, and the jib is stowed on one side of a base boom of the telescopic boom when the jib is not used.
In a jib crane vehicle of this type, the operations to extend and stow the jib are performed as described below.
First, in a jib stowage position, a boss (with a pin hole) on a distal portion of the top boom and a boss (with a pin hole) on a proximal portion of the jib are uncoupled, and the jib is supported in a position extending along one side of the base boom by first stowing means located on the distal side on the base boom and second stowing means located on the proximal side on the base boom. To bring the jib from the stowage position to the extended position, the telescopic boom is fully contracted and the second stowing means on the proximal side on the base boom is uncoupled. Then, bosses on a first side portion of the top boom distal portion and bosses on a first side portion of the jib proximal portion are aligned with each other and these bosses are coupled to each other by a common pivot pin. Next, the first stowing means on the distal side on the base boom is uncoupled and the jib is rotated to the front of the top boom distal portion about the pivot pin. Then, bosses (with a pin hole) on a second side portion of the top boom distal portion and bosses (with a pin hole) on a second side portion of the jib proximal portion are aligned with each other and the bosses are coupled to each other by a coupling pin.
When the jib is brought from the stowage position to the extended position, the telescopic boom is fully contracted and the coupling pin on the non-pivot side between the top boom distal portion and the jib proximal portion is pulled out. Then, the jib is rotated into a space on one side of the telescopic boom about the pivot pin coupling the bosses on the first side portion of the top boom distal portion and the bosses on the first side portion of the jib proximal portion until the jib lies along a lateral side of the base boom, and a lateral side of the jib is coupled to the lateral side of the base boom by the first stowing means located on the distal side on the base boom. Then, the pivot pin that couples the top boom distal portion and the jib proximal portion is pulled out, and a distal portion of the jib is coupled to a proximal portion of the base boom by the second stowing means located on the proximal side on the base boom.
When the jib is extended to the front of the top boom distal portion from the stowage position, it is very dangerous to uncouple the first stowing means by mistake when the bosses on the top boom distal portion and the bosses on the jib proximal portion are not coupled with each other by the pivot pin, because there is a possibility of the jib falling off. Especially, when the first stowing means is configured to be manually operated from below the jib, the possibility of the jib falling off could lead to a physical injury.
Therefore, the applicant of the present invention has proposed a jib stowing device in which the first stowing means cannot be uncoupled unless the boss on the top boom distal portion and the boss on the jib proximal portion are coupled by the pivot pin (JP-A-2003-226486 as Patent Document 1). The jib stowing device of Patent Document 1, which is shown in FIG. 12 to FIG. 15, is constituted as described below.
The jib stowing device of the related art (Patent Document 1) includes bosses (14a and 14b) with a pin hole provided on a first side portion of a distal portion 13 of a top boom 12 of a telescopic boom 1 and bosses (24a and 24b) with a pin hole provided on a first side portion of a proximal portion 23 (jib support) of a jib 2 which are removably couplable to each other by means of a pivot pin 30 (upper pivot pin 31 and a lower pivot pin 32), and first stowing means A provided between a distal position on a lateral side of a base boom 11 of the telescopic boom 1 and a proximal position of a lateral side of the jib 2 as shown in FIG. 12 to FIG. 13. Second stowing means (not shown) for coupling a distal portion of the jib to the base boom is provided between a distal lateral side of the jib 2 and a proximal lateral side of the base boom 11.
The bosses (14a and 14b) on the top boom distal portion 13 and the bosses (24a and 24b) on the jib proximal portion 23 are provided at two locations vertically separated from each other as shown in FIG. 13. That is, the bosses on the top boom distal portion 13 includes an upper boss 14a and a lower boss 14b (one each), and the bosses on the jib proximal portion 23 includes upper bosses 24a and lower bosses 24b (two each).
The pivot pin 30 includes a threaded rod 33, and an upper pivot pin 31 and a lower pivot pin 32, each of which is formed of a female-threaded cylinder, threaded over upper and lower portions, respectively, of the threaded rod 33 as shown in FIG. 13. Threads running in the opposite directions are formed on the upper and lower halves of the threaded rod 33, and the upper pivot pin 31 and the lower pivot pin 32 are threaded on the oppositely threaded portions. Therefore, by rotating a lower end of the threaded rod 33 to the right or left with a rotary tool, the upper and lower pivot pins 31 and 32 can be moved toward (in a pin retracting direction) or away from (in a pin inserting direction) each other.
The pivot pin 30 is located between the upper and lower bosses 24a and 24b on the jib proximal portion 23. In the jib stowage state, the upper pivot pin 31 and the lower pivot pin 32 are retracted out of the upper boss 14a and the lower boss 14b, respectively, on the top boom distal portion 13 (the coupling between the top boom distal portion 13 and the jib proximal portion 23 is released) when the upper and lower pivot pins 31 and 32 are operated in a direction toward each other, and the upper pivot pin 31 and the lower pivot pin 32 are inserted into the upper boss 14a and the lower boss 14b, respectively, on the top boom distal portion 13 (the top boom distal portion 13 and the jib proximal portion 23 are coupled to each other) when the upper and lower pivot pins 31 and 32 are operated in a direction away from each other.
As shown in FIG. 13, the first stowing means A has upper bosses (with a pin hole) 17a and lower bosses (with a pin hole) 17b provided at two vertically separated locations on a lateral side of the base boom 11 (FIG. 12), an upper boss (with a pin hole) 27a and a lower boss (with a pin hole) 27b provided at two vertically separated locations on a lateral side of the jib 2, upper and lower coupling pins 41 and 42 for coupling and uncoupling the upper and lower bosses (17a and 27a, and 17b and 27b), and a hydraulic cylinder 45 for moving the upper and lower coupling pins 41 and 42 toward and away from each other. The hydraulic cylinder 45 is disposed with its tube 46 located above its rod 47. The upper coupling pin 41 is connected to the upper end of the tube 46, and the lower coupling pin 42 is connected to the lower end of the rod 47. The hydraulic cylinder 45 and the upper and lower coupling pins 41 and 42 are attached to the base boom 11.
When the jib 2 is laid along the base boom 11 as shown in FIG. 12, the upper bosses 17a on the base boom 11 and the upper boss 27a on the jib 2, and the lower bosses 17b on the base boom 11 and the lower boss 27b on the jib 2 are aligned with each other as shown in FIG. 13. When the hydraulic cylinder 45 is extended with the upper and lower bosses aligned with each other, the upper coupling pin 41 is inserted into the upper bosses 17a and 27a and the lower coupling pin 42 is inserted into the lower bosses 17b and 27b (the first stowing means A is brought into a coupled state). On the other hand, when the hydraulic cylinder 45 is contracted from the state where the upper and lower coupling pins 41 and 42 couple the upper and lower bosses, respectively, the upper and lower coupling pins 41 and 42 are retracted out of the upper and lower bosses 27a and 27b on the jib and the first stowing means A is brought into an uncoupled state.
In addition, the jib stowing device of the related art is provided with pivot pin insertion state detecting means 5 for detecting whether or not the upper and lower pivot pins 31 and 32 are inserted in the upper and lower bosses 14a and 14b, respectively, on the top boom distal portion 13, coupling pin retraction restricting means 8 for restricting the upper and lower coupling pins 41 and 42 of the first stowing means A from being retracted out of the upper and lower bosses 27a and 27b on the jib 2, and associating means (control cable) 91 for associating the pivot pin insertion state detecting means 5 and the coupling pin retraction restricting means 8 as shown in FIG. 13 and FIG. 14.
The control cable 91 as the associating means has an outer casing 92 and an inner cable 93 movably received in the outer casing 92.
As the pivot pin insertion state detecting means 5, a protrusion 51 secured to the upper pivot pin 31 is employed. The protrusion 51 can move vertically in accordance with vertical movement of the upper pivot pin 31 to detect the insertion state of the upper and lower pivot pins 31 and 32. In the related art, because the upper and lower pivot pins 31 and 32 are simultaneously moved toward or away from each other by the threaded rod 33, the insertion state of both the pivot pins 31 and 32 can be detected by detecting vertical movement of one of the pivot pins (upper pivot pin 31).
A first end 93a of the inner cable 93 of the control cable 91 is coupled to the protrusion 51 as the pivot pin insertion state detecting means 5, and the inner cable 93 is pushed or pulled relative to the outer casing 92 when the protrusion 51 moves vertically.
The coupling pin retraction restricting means 8 has a restricting member 81 which can retractably enter a gap S between the lower end of the tube 46 of the hydraulic cylinder 45 and the upper end of the lower coupling pin 42 as shown in FIG. 13 and FIG. 14. The restricting member 81 has a vertical length which is slightly smaller than the width of the gap S between the lower end of the cylinder tube 46 and the upper end of the lower coupling pin 42 at the time when the hydraulic cylinder 45 has been extended. Also, the restricting member 81 is swingably pivoted by a shaft 82 on a mounting base 26 attached to the jib 2 at the first stowing means A. The restricting member 81 is urged in a restricting direction (direction toward the cylinder rod 47) as indicated by solid lines in FIG. 14 by a spring 85 (FIG. 14). In addition, a second end 93b of the inner cable 93 of the control cable 91 is coupled to the restricting member 81, and the restricting member 81 is displaced to a non-restricting position (reference numeral 81) indicated by dotted lines in FIG. 14 against the urging force of the spring 85 when the inner cable 93 is pulled as a result of vertical movement of the protrusion 51.
The jib stowing device of the related art shown in FIG. 12 to FIG. 14 functions as shown in FIGS. 15(A) and (B).
First, when the upper and lower pivot pins 31 and 32 are not inserted in the upper and lower bosses 14a and 14b on the top boom distal portion 13 (the pivot pin 30 is in a contracted state), the restricting member 81 is positioned in the gap S between the lower end of the cylinder tube 46 and the upper end of the lower coupling pin 42 by the urging force of the spring 85 as shown in FIG. 15(A) because the protrusion 51 is located at its lowered position and the pulling effect of the control cable 91 (inner cable 93) does not act on the restricting member 81. In the state shown in FIG. 15(A), because the restricting member 81 is positioned in the gap S, the restricting member 81 in the gap S prevents the hydraulic cylinder 45 from contracting even if the hydraulic cylinder 45 is operated to the contraction side. As a result, the upper and lower coupling pins 41 and 42 are not retracted out of the upper and lower bosses 17a and 17b on the jib 2 (the coupled state of the first stowing means A is maintained).
On the other hand, when the upper and lower pivot pins 31 and 32 are inserted in the upper and lower bosses 14a and 14b on the top boom distal portion 13 (the pivot pin 30 is in an extended state) as shown in FIG. 15(B), the pulling effect of the control cable 91 (inner cable 93) acts on the restricting member 81 because the protrusion 51 is located in its raised position, and the restricting member 81 is positioned outside the gap S between the lower end of the cylinder tube 46 and the upper end of the lower coupling pin 42 against the urging force of the spring 85 (the state indicated by reference numeral 81′ in FIG. 14). In the state shown in FIG. 15(B), the hydraulic cylinder 45 can be contracted, and the upper and lower coupling pins 41 and 42 can be retracted out of the upper and lower bosses 27a and 27b on the jib 2 by contracting the hydraulic cylinder 45.
In the jib stowing device according to the related art constituted as described above (FIG. 12 to FIG. 15), when the jib 2 is extended forward from the stowed state along the base boom 11 (the state shown in FIG. 15(A)), the upper and lower coupling pins 41 and 42 of the first stowing means A are retracted out of the upper and lower bosses 27a and 27b on the jib 2 after the upper and lower pivot pins 31 and 32 have been inserted into the upper and lower bosses 14a and 14b on the top boom distal portion 13 as shown in FIG. 15(B). At this time, even if the upper and lower coupling pins 41 and 42 of the first stowing means A are retracted (the hydraulic cylinder 45 is contracted) by mistake with the upper and lower pivot pins 31 and 32 in the retracted state, the upper and lower coupling pins 41 and 42 cannot be retracted (pulled out) because the restricting member 81 is in the restricting position.
Therefore, the jib stowing device of the related art has a function of preventing the pivot pins (31 and 32) and the coupling pins (41 and 42) from being retracted (pulled out) simultaneously during a jib extending operation to secure safety during a jib extend operation.    Patent Document 1: JP Patent Application Publication No. 2003-226486